ThermaSol Fortis Outdoor Sauna Cabin (3-4 Person)

A Sanctuary at the End of the Garden

Some retreats you travel to. This one waits in your own backyard.

The Fortis is a fully assembled outdoor cabin with a clean, modern silhouette - a low eave-style roofline and a tinted glass front that reads as architecture, not equipment. Thermally modified Nordic spruce and pinewood wrap the exterior in warm, brushed grain, set against honed black trim and aluminum cladding; the result sits as comfortably beside a contemporary home as a rustic one. Step through the aluminum-framed glass door and the world goes quiet behind 8mm Parsol dark-grey glass - light comes in, but the space stays yours.

Inside, brushed thermally modified wood walls meet smooth thermo-aspen benches, a material chosen because it stays stable and resists moisture season after season. The 8kW Harvia Virta builds a deep, even heat - adjustable up to 194°F - and the Harvia Xenio touchpad lets you schedule sessions, set a delay start, and pre-heat from your phone through the MyHarvia app, so the cabin is warm by the time you walk out to it. RGB LED lighting with a remote sets the mood from soft and low to bright and clear.

It's built to stay outside and shrug off the weather: multi-layer wood-fiber insulation for year-round efficiency, a durable weather-resistant roof, integrated rainwater management, and argon-insulated, UV-protected tempered glass. The Fortis arrives fully assembled on a flatbed - no panel-by-panel build - though at over a ton it's placed by crane or forklift and wired by a licensed electrician, so it's a planned installation rather than a same-afternoon setup.

For the home where wellness isn't a room you visit but a structure you walk out to - a quiet, beautiful fixture of the life you live outdoors.

• Fully assembled outdoor cabin with a tinted glass front - architectural, private, and light-filled
• Thermally modified Nordic spruce/pinewood exterior with honed black trim and aluminum cladding
• Brushed thermally modified wood interior walls with smooth thermo-aspen benches and backrest
• 8mm Parsol dark-grey glass - argon-insulated, UV-protected, for privacy and thermal efficiency
• 8kW Harvia Virta heater (up to 194°F) with Harvia Xenio Wi-Fi control + MyHarvia app
• 12-hour delay start and weekly scheduling - pre-heat on your terms
• RGB LED lighting with remote for personalized mood lighting
• Multi-layer wood-fiber insulation + durable weather-resistant roof with integrated rainwater management - built for all seasons
• Aluminum-framed glass door with hidden hinges
• Seats 3-4
• Arrives fully assembled; requires crane/forklift offload and licensed-electrician hookup
• Included: sauna stones, control, sensor, 2 headrests, and wood platform

Sauna use isn't right for everyone. Consult your physician before use, especially if you are pregnant or have a heart condition, high or low blood pressure, or any cardiovascular or other medical concern. Begin with shorter, lower-heat sessions, hydrate, avoid alcohol before use, don't exceed ~30 minutes, and supervise children. Use only clean water on the stones. Install outdoors on a firm, level surface, keep the air outlet unobstructed, and have the heater wired by a licensed electrician.

• Free shipping in the continental US; cost quoted by location
• Delivered fully assembled via flatbed trailer, ~12-13 weeks; notified ~2 weeks ahead
• This is a large, heavy unit (assembled ~2,161 lbs; shipping ~2,381 lbs) - a forklift or crane is required for offloading and placement. Manual offloading is not recommended; have the proper equipment on site at delivery
• The path from the delivery point to the placement site must be clear and accessible for that equipment
• Plan your space: the cabin is 90" L x 87" W x 89" H; allow placement clearance of 110" W x 106" D x 95" H, on an open outdoor site with no landscape or tree obstructions
• Install on a firm, level surface with slight runoff for drainage - concrete, decking, pavers, or compacted gravel. For a concrete slab, an 8" minimum thickness is recommended; the slab must be level and able to carry the full installed load
• If installing on an existing deck or platform, verify the structure can safely support the combined weight of the cabin, occupants, and equipment
• Electrical: the 8kW Harvia Virta requires a dedicated 240V, 40-amp circuit; lighting runs on 110V. All electrical work must be completed by a licensed electrician
• Ventilation: the air outlet must remain unobstructed and easily accessible

Download the ThermaSol Fortis specification sheet (PDF)

Is the Fortis an indoor or outdoor sauna?
Outdoor. It's a fully assembled, all-season cabin built to live outside, with a weather-resistant roof, insulated construction, and UV-protected tinted glass.

How many people does it seat?
Three to four, with a 54 sq ft interior.

Does it really arrive fully assembled?
Yes - it ships fully assembled on a flatbed trailer, so there's no panel-by-panel build. Because it weighs over a ton, a forklift or crane is required to offload and place it, and a licensed electrician wires the heater. Plan it as a scheduled installation rather than a same-day setup.

What surface can I put it on?
A firm, level surface with slight runoff for drainage - concrete, decking, pavers, or compacted gravel. For a concrete slab, an 8" minimum thickness is recommended and it must carry the full installed load. On an existing deck, verify the structure can support the combined weight of the cabin, occupants, and equipment.

How much room do I need?
Beyond the cabin footprint, allow a placement clearance of 110" W x 106" D x 95" H, on an open outdoor site with no landscape or tree obstructions, plus a clear, accessible path for the crane or forklift.

What electrical setup does it need?
The 8kW Harvia Virta heater needs a dedicated 240V, 40-amp circuit; the lighting runs on 110V. All electrical work must be completed by a licensed electrician.

Is it built for cold-weather / year-round use?
Yes. Multi-layer wood-fiber insulation, a durable weather-resistant roof with integrated rainwater management, and argon-insulated glass are designed for all-season performance.

Can I control it from my phone?
Yes - the Harvia Xenio control offers a 12-hour delay start, weekly scheduling, and Wi-Fi control through the MyHarvia app, so it's hot when you want it.

What's included?
Sauna stones, the control and temperature sensor, two headrests, a wood platform, and MyHarvia app access. Optional accessories (pail and ladle, cushions, aromatherapy, decorative stones, timer) are available.

What's the warranty?
The sauna structure carries a 1-year limited warranty against manufacturing defects from completion of installation. The Harvia heater, Xenio control, and power box are covered for 5 years in residential use (stones and heating elements, 1 year). To keep coverage valid, the sauna must be installed by a certified electrician and registered within 15 days of purchase. Full terms at thermasol.com/pages/warranty.